This invention relates to an equipment for determining the position of a metal body in a medium with low electric conductivity, which comprises:
a support, PA0 a radiating self-induction coil mounted on the support, PA0 two receiving self-induction coils mounted on the support, said coils having parallel axes, the receiving coils being arranged symmetrically relative to the radiating coil, and the symmetry planes of the receiving coils at right angle to the axes thereof coinciding with one another and differing from the symmetry plane of the radiating coil at right angle to the axis thereof, PA0 a connection to a current source for said radiating coil, PA0 signaling members, and PA0 a connection between the receiving coils and said signaling members.
An equipment of this kind is known from U.S. Pat. No. 2,228,293. In the embodiment according to FIG. 3 in this patent, the equipment comprises three radiating coils lying respectively on the three legs of an E-shaped core. Said coils are fed with D.C. and are series connected in such a way that the magnetic flux generated in the center coil has the opposite polarity relative to that magnetic flux generated in the other coils. Two receiving or sensing coils, series-connected, are mounted on the outer core arms in the extension of the radiating coils mounted thereon. The equipment comprises means sensing the changes in the voltage being induced in the receiving coils due to changes in the reluctance of the magnetic field being generated by the movement of a metal body inside said field.
Said equipment which is designed to sense a metal object inside a moving mass, does not allow localizing a metal body inside a material with a low electric conductivity with a high accuracy as required when performing operations on human bodies, which lies for example in the range of a fraction of millimeter. Moreover, the relative arrangement of the coils in this known equipment is such as to prevent arranging the support with the coils thereof in a suitable position for the strength of the signal controlling the signaling members to increase together with the lack of symmetry of the metal object relative to the coils.
The invention has for an object to provide an equipment which allows due to the mechanical and electric design thereof, an optimum localizing of a metal object.